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what is the best way to weld this

06-07-2011, 02:23 PM

I have an exhausting system replacing the factory cat with high flow cat... the flanges have sleeves, it slips right over the cutted downpipe where the cat used to attached to... it has a little rust, it is steel / aluminuzed steel ? the sleeve over is stainless.... since it fitted over with a little gap. between old a little rust and new pipe. what is the best process , recommendations ?

I have acess: Mig with carbon steel / flux or gassed. or Tig dynasty 200DX with 309L 308L or carbon wires , or silicon rods ?

Comment

The aluminum here is the killing agent in the steel and/or a corrosion prevention coating. Aluminum killed steels weld just fine, only difference is the aluminum oxide won't melt in the weld and form a tiny slag bead like silicon killed steels. And Al killed steels are finer grain with slightly better corrosion resistance.

Aluminized steel has a mechanically-applied coating of aluminum which acts like the zinc coating in galvanized steel. Only aluminum won't vaporize as easily, zinc will rapidly degrade/vaporize under exhaust heat.

Metal fume issues are not present with aluminized steels don't have the dangers of galvanized/zinc coated products, most weldable primers like Deoxaluminite are aluminum based.

Finally, killed steel refers to the lack of free oxygen in the final mill product. Steel is borne from the basic oxygen process which takes molten cast iron (4%+ carbon dissolved in iron) and bubbles oxygen through it to burn out the carbon. This leaves the iron with less than 1% carbon but it also fizzes like a soft drink since residual oxygen and carbon monoxide are present. Silicon, aluminum and or manganese are added which strongly combine with the oxygen and carbon monoxide, making the steel "quiet" or "killed". If you have ever welded mystery steel which bubbles, pops and causes issues even when perfectly clean, that is probably non-killed steel. It is frustrating, especially with sheet products.